There are a number of method and apparatus for object detection and human recognition, but a robust solution for general human detection when the face is not visible and in varied conditions remains elusive.
U.S. Pat. No. 6,697,502 B2 discloses a digital image processing method for detecting human figures in a digital color image, comprising the steps of: providing a digital color image having pixels representing RGB values; segmenting the image into non-overlapping regions of homogeneous color or texture; detecting candidate regions of human skin color; detecting candidate regions of human faces; and for each candidate face region, constructing a human figure by grouping regions in the vicinity of the face region according to a pre-defined graphical model of the human figure, giving priority to human skin color regions. As can be seen, the said method relies on visibility of face and skin color as a pre-requisite. The said method however discloses the advantage that clothed, unknown figures can be more reliably detected in the digital image.
U.S. Pat. No. 8,228,382 B2 discloses a system and method for detecting and counting people in a specified area. The method assumes that the head is elliptical in shape with a width of X and height of 1.5X and once detected, the skin color analysis is done on this shape.
US20070237387 A1 discloses a method and system for detecting humans in images of a scene acquired by a camera. Gradients of pixels in the image are determined and sorted into bins of a histogram. An integral image is stored for each bin of the histogram. Features are extracted from the integral images, the extracted features corresponding to a subset of a substantially larger set of variably sized and randomly selected blocks of pixels in the test image. The features are applied to a cascaded classifier to determine whether the test image includes a human or not.
US20130251203 A1 discloses a person detection device with which it is possible to estimate a state of a part of a person from an image. A person detection device comprises: an evaluation unit which acquires a prescribed outline of a person from an evaluation image; and a shoulder position calculation unit and an orientation estimation unit which estimate a state of a prescribed part of a person which is included in the evaluation image from the prescribed outline of the person which is acquired from the evaluation image, on the basis of an estimation model which denotes a relation between the prescribed outline and the state of the prescribed part of the person.
US20140139660 A1 describes the method and apparatus for detecting people by confirming an omega shape for head and shoulder. The omega shape is determined by first finding convex hull points on right and left parts using Graham Scan, thereafter finding the head and shoulder points and subsequently finding the neck points on each side.
US20130243259 A1 describes the method and apparatus for object detection of information regarding object having joints. For the omega shape, it first generates a distance histogram along the Y-axis of the omega shape. Thereafter, by applying a pre-determined threshold on the distance histogram, the shoulder part is eliminated and the head part remains. From this, the centre of the head is calculated and a pre-determined ratio or body constraint information is used to calculate the shoulder points on each side.
From the above mentioned, it is clear that some prior art methods rely on the visibility of face or skin as a pre-requisite for detection of human images. Other prior art methods uses shape i.e. omega shape as key differentiating factors for humans. The existing prior art methods do not seem to address the non-ideal scenarios that includes imperfect positions and asymmetric shape that are available from a live image, as the human could be at different angles with respect to a surveillance camera and the outline obtained may not be perfect depending on the lighting and the background conditions.
The present invention aims to overcome the disadvantages of the prior art. The present invention is based on shape of the upper body comprising head and the upper torso, which is omega shape and the methods are developed to address various non-idealistic conditions. It includes scenarios where the front of the human is facing the camera or the side or back of the human is facing the camera. It takes into account tilted head, shoulder asymmetry and the fact that human in the intended scenarios may not be standing upright. Hence, the method and apparatus of the present invention overcomes the disadvantages mentioned in the prior art and have the ability to address non-ideal scenarios more robustly.